Multilayer ceramic substrate and electronic device

Abstract

A multilayer ceramic substrate that includes a first layer positioned at a surface of the multilayer ceramic substrate, a second layer adjacent the first layer and positioned inward of the first layer, and a surface layer electrode disposed on a surface of the first layer. The first layer has a porosity of 13% or less and a maximum pore size of 10 μm or less. The second layer has a porosity of 14% or less and a maximum pore size of 11 μm or less.

The invention claimed is: 
     
       1. A multilayer ceramic substrate comprising:
 a first layer positioned at a surface of the multilayer ceramic substrate, the first layer having a first porosity of 13% or less and a first maximum pore size of 10 μm or less, and having a first composition containing a first metal oxide that is at least one selected from CuO and Ag 2 O; 
 a second layer adjacent the first layer and positioned inward of the surface of the multilayer ceramic substrate, the second layer having a second porosity of 14% or less and a second maximum pore size of 11 μm or less, and having a second composition containing a second metal oxide that is at least one selected from CuO and Ag 2 O; and 
 a surface layer electrode disposed on a surface of the first layer, wherein 
 the first composition of the first layer is different from the second composition of the second layer, and 
 a first amount of the first metal oxide in the first layer is larger than a second amount of the second metal oxide in the second layer. 
 
     
     
       2. The multilayer ceramic substrate according to  claim 1 , wherein the first porosity is 8% or less. 
     
     
       3. The multilayer ceramic substrate according to  claim 2 , wherein the first maximum pore size is 7 μm or less. 
     
     
       4. The multilayer ceramic substrate according to  claim 1 , wherein the first maximum pore size is 7 μm or less. 
     
     
       5. The multilayer ceramic substrate according to  claim 1 , wherein the first maximum pore size is 1 μm to 10 μm. 
     
     
       6. The multilayer ceramic substrate according to  claim 1 , wherein the first porosity is 1% to 13%. 
     
     
       7. The multilayer ceramic substrate according to  claim 1 , wherein the second porosity is 9% or less. 
     
     
       8. The multilayer ceramic substrate according to  claim 1 , wherein the second porosity is 2% to 14%. 
     
     
       9. The multilayer ceramic substrate according to  claim 1 , wherein the second maximum pore size is 2 μm to 11 μm. 
     
     
       10. The multilayer ceramic substrate according to  claim 5 , wherein the second maximum pore size is 9 μm or less. 
     
     
       11. The multilayer ceramic substrate according to  claim 1 , wherein the second maximum pore size is 9 μm or less. 
     
     
       12. The multilayer ceramic substrate according to  claim 1 ,
 wherein a first thermal expansion coefficient of the first layer is lower than a second thermal expansion coefficient of the second layer, 
 the first composition of the first layer further contains glass containing 40 weight % to 65 weight % of at least one selected from CaO, MgO, SrO, and BaO, and alumina; and 
 the second composition of the second layer further contains glass containing 40 weight % to 65 weight % of at least one selected from CaO, MgO, SrO, and BaO, and alumina, 
 an amount of the alumina in each of the first composition and the second composition is 35 weight % to 60 weight % relative to a total weight of the glass and the alumina, 
 an amount of the first metal oxide is 1 weight % to 10 weight % relative to the total weight of the glass and the alumina in the first composition, and 
 an amount of the second metal oxide is 1 weight % to 10 weight % relative to the total weight of the glass and the alumina in the second composition. 
 
     
     
       13. The multilayer ceramic substrate according to  claim 1 , wherein a first thermal expansion coefficient of the first layer is lower than a second thermal expansion coefficient of the second layer, and when the first thermal expansion coefficient of the first layer is expressed as α1 [ppmK −1 ] and the second thermal expansion coefficient of the second layer is expressed as α2 [ppmK −1 ], 0.3 ≤α2−α1≤1.5. 
     
     
       14. An electronic device comprising the multilayer ceramic substrate according to  claim 1 . 
     
     
       15. The multilayer ceramic substrate according to  claim 1 , wherein a first thermal expansion coefficient of the first layer is lower than a second thermal expansion coefficient of the second layer. 
     
     
       16. The multilayer ceramic substrate according to  claim 1 , wherein
 the first composition of the first layer further contains glass containing 40 weight % to 65 weight % of at least one selected from CaO, MgO, SrO, and BaO, and alumina; and 
 the second composition of the second layer further contains glass containing 40 weight % to 65 weight % of at least one selected from CaO, MgO, SrO, and BaO, and alumina. 
 
     
     
       17. The multilayer ceramic substrate according to  claim 16 , wherein
 an amount of the alumina in each of the first composition and the second composition is 35 weight % to 60 weight % relative to a total weight of the glass and the alumina, 
 an amount of the first metal oxide is 1 weight % to 10 weight % relative to the total weight of the glass and the alumina in the first composition, and 
 an amount of the second metal oxide is 1 weight % to 10 weight % relative to the total weight of the glass and the alumina in the second composition.